3.0. Introduction

Aligning UI components has always been a big headache for programmers. Most of the
view controllers in complex iOS apps contain a lot of code just to set the
frame of UI components on the screen, align components
horizontally/vertically, and make sure the components look good on
different iOS versions. Not only that, but some programmers want to also
use the same view controllers across various devices such as iPhones and
iPads. This adds a lot of complexity to the code. Apple has made it easier
for us in iOS 6. They have brought Auto Layout from OS X over to iOS. We
will be talking about the details of Auto Layout in a moment, but let me
just give you a brief introduction to it and explain what it is
for.

Let’s say you have a button that you want to keep at the center of
the screen. The relation between the center of the button and the center
of the view on which it resides can be simply described like so:

Button’s center.x is equal to view’s center.x

Button’s center.y is equal to view’s center.y

Apple noticed that a lot of the positioning of UI components can be
solved with a simple formula:

object1.property1 = (object2.property2 * multiplier) + constant value

For instance, using this formula, I could simply center a button on
its superview like so: